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• <br />HYDROLOGIC DOCUMENTATION <br />SMALL AREA EXEMPTION <br />OFFICE/PARKING LOT/LEACH FIELD <br />The following calculations demonstrate the amount of sediment fence surface area required to adequately handle <br />the runoff from [he office, parking area, and leach field area. <br />Runo0~pcak discharge calculations were performed utilizing the SEDCAD+ computer model consistent with the <br />methodology previously discussed . The sediment fence was designed to handle the peak discharge from a 10- <br />year, 24-hour storm event. <br />Hvdroloev Inputs <br />The curve numbers (CN) used were obtained from Procedures for Determining Pe•tk Flows in Colorado and <br />Technical Release No. 55. Based on soil type and vegetation cover, curve numbers were deternined for the <br />following condition. <br />Undisturbed <br />Soil Type: C <br />Ground Cover: Fair <br />Cover Type: Pasture Land <br />CN: 79 <br />I'~ <br />U <br />• <br />Disturbed <br />Soil Type: C <br />Ground Cover- Dirt Road <br />Cover Type: None <br />CN: 89 <br />All other hydrology inputs are shown on the attached SEDCAD+ computer printouts <br />Llydre I~gy Results <br />Peak Discharge: <br />Sediment Fence Requirements <br />Sediment Fence Pemiissivit}•: <br />Required Surface Arca: <br />0.5 cfs <br />I S gal/min/RZ or 0.033 cfs/ft'- <br />0.5 cfs/0.033 cfs/Q2= IS fl' <br />The required length of fence should be determined assuming flow depth of 1 foot. Ach~al fence installation <br />should be a minimum of 1.5 feet to allo++• for Geeboard and a factor of safeh• on the permissivity. <br />`TQ-o ~ <br />SuB/n,~rTAL D/iTE 1~-~17~46 <br />